Linerless plastic closure with a sealing lip

ABSTRACT

A cap, which can be attached to a container having an annular opening, includes a top wall and an annular skirt portion. The top wall includes an inner surface and rigid sealing members which seal an inner and outer edge of the opening through the engagement of first and second rigid members with edges of the opening and which exert a force on the container to cause the container to attach in a proper position. The annular skirt portion, disposed along an outer circumference of the top wall and extending downwards, includes internal threads configured to seal the cap onto the container, longitudinal ribs for increasing the friction on the annular skirt portion, and a pilfer band.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a linerless plastic cap for a beverage container, comprising a top wall portion with a sealing lip which engages with the rim of an opening of a container and an annular skirt portion having internal threads configured to engage with external threads on the outer surface of an opening of a container so as to secure the cap on the opening.

[0003] 2. Discussion of the Background

[0004] Plastic closures (hereinafter “caps”) are well known and are suitable for closing and sealing the contents of containers. In particular, these devices are widely used to seal bottles containing carbonated and non-carbonated beverages (as in U.S. Pat. No. 4,429,802), condiments, and other food products, although they may be used on non-food products, such as motor oil or pharmaceuticals, as well.

[0005] Various cap constructions have been known for a number of years and special design considerations have been made in order to increase the sealing properties and to facilitate the opening of the containers. For the beverage market, it is particularly desirable to have a cap that guarantees hermetic properties of the contents of the container. Such caps generally have an improved integral seal.

[0006] One known way to provide an integral seal was to provide a liner in the cap. This liner was constructed of a soft plastic or synthetic that, when the cap was tightened onto the container, created a tight seal around the opening of the container.

[0007] However, lined caps presented various manufacturing problems. Among these are the added cost of the material of the liner, and the cost and time of the manufacturing step of installing the liner.

[0008] Consequently, various configurations of linerless caps have been tested. Among them, U.S. Pat. No. 4,905,852 describes such a linerless cap. The '852 patent provides a plastic closure having a top wall, an internally threaded sidewall, and a seal. The seal comprises outer and inner concentric sealing members extending downwardly from an inner surface of the top wall. The outer sealing member extends downwardly farther than the inner sealing member and is substantially thicker than the inner sealing member. The outer sealing member has an outer side surface that extends downwardly and inwardly and has an inner side surface that extends downwardly and outwardly. The inner sealing member has outer and inner side surfaces that extend downwardly and inwardly. The inner side surface of the outer sealing member is disposed to engage an outer corner of the rim of the mouth of the bottle when the closure is threaded onto the bottle, and the inner sealing member is disposed to engage the top of the rim after engagement of the corner with the inner surface of the outer sealing member. The outer sealing member is adapted to deflect outward slightly due to the engagement of its inner side surface with the corner of the rim, and is substantially more rigid than the inner sealing member. The inner sealing member is adapted to deflect upwardly and inwardly to form a top seal on the rim. Movement of the top wall of the closure toward the rim is limited so that when the closure is fully threaded onto the bottle, a space remains between the inner surface of the inner sealing member and the inner surface of the top wall of the closure.

[0009] Caps such as the one discussed above have certain inherent disadvantages. Among these disadvantages are inadequate sealing characteristics which arise from a tendency of the seal on the cap to fail to properly engage with the rim of the opening of the container. Particularly, in the seal of the patent noted above, it is possible that, due to the circular construction of the inner seal, when the cap is tightened onto the opening, the inner seal will not simply bend inwardly as designed. Rather, it may crumple due to the lack of room for the circular seal to deform into. Thus, the crumpled seal will actually prevent a good seal from being created.

[0010] Another disadvantage is the tendency for caps to be misaligned during the final stages in which the cap is tightened around the opening. Such a situation arises from local discontinuities in either the seal on the cap or on the edge of the opening.

[0011] Consequently, there exists a need for a linerless cap with a sealing lip for sealing the opening of a container which creates a hermetic seal around the rim of the opening of the container between the atmosphere and the contents of the container and which decreases the likelihood that the cap will fail to engage the rim of the opening of the container in the correct position.

SUMMARY OF THE INVENTION

[0012] It is an object of the invention to provide a linerless cap with a sealing lip for sealing the opening of a container, which creates a hermetic seal around the rim of the opening of the container between the atmosphere and the contents of the container and which decreases the likelihood that the cap will fail to engage the rim of the opening of the container in the correct position.

[0013] According to a first aspect of the invention the above and other features of the invention are provided by a cap that can be attached to a container having an annular opening. The cap comprises a top wall comprising an inner surface including a sealing lip having first and second rigid members which, in a direction from a point between them to tops thereof, taper away from one another. The rigid members are configured to provide a bidirectional centering force on the opening of the container. The cap further provides an annular skirt portion along an outer circumference of the top wall.

[0014] According to a second aspect of the invention the above and other features of the invention are provided by a cap that can be attached to a container having an annular opening. The cap comprises a top wall comprising an inner surface including a sealing lip having first and second rigid members of substantially equal rigidity. The cap further provides an annular skirt portion along an outer circumference of the top wall.

[0015] According to a third aspect of the invention the above and other features of the invention are provided by a cap which can be attached to a container having an annular opening. The cap comprises a top wall comprising an inner surface including a means for providing a bidirectional centering force on the opening of the container. The cap further provides an annular skirt portion along an outer circumference of the top wall.

[0016] An exemplary embodiment of this invention provides for a cap which covers an opening of a container and which can be removed and attached multiple times. The cap includes a top wall portion having an inner surface and a sealing lip attached to the inner surface. An annular skirt portion is disposed on the outer edge of the top wall portion and extends over the opening of the container when the cap is attached to the container. Internal threads on the annular skirt portion engage with external threads on the opening of the container to secure the cap on the opening.

[0017] The sealing lip forms a hermetic seal around the rim of the opening which prevents leakage between the container and the atmosphere outside. Moreover, because the sealing lip has a cross-sectional shape resembling a pair of triangles spaced apart from each other, the sealing lip tends to force the rim of the opening into the proper position for sealing to occur.

[0018] The cap is sealed onto the container by positioning the cap at the edge of the opening of the container and turning the cap so internal threads on the annular skirt portion engage with external threads on an outer surface of the opening, thereby tightening the cap on the opening until a rim of the opening forms a hermetic seal with the sealing lip.

[0019] Among the benefits accrued by using the current invention is an improvement in the sealing properties of known linerless plastic closures.

[0020] Another benefit is that, as noted above, the relatively rigid sealing lip acts to provide a self-centering action for the cap during attachment to the container. Thus, the reliability of the cap is increased.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] A more complete appreciation of the invention and many of the attendant advantages thereof will become readily apparent with reference to the following detailed description particularly when considered in conjunction with the accompanying drawings, in which:

[0022]FIG. 1 is a side view of the opening of a container upon which the present invention is attached.

[0023]FIG. 2 is an exploded view of the sealing lip as connected to the inner surface of the top wall portion of the cap.

[0024]FIG. 3 is a bottom view of the cap along the line III-III in FIG. 1.

[0025]FIG. 4 is an enlarged bottom view of the cap along the line IV-IV in FIG. 2.

[0026]FIG. 5a is an enlarged side view of the rim of the opening approaching the sealing lip during attachment.

[0027]FIG. 5b is an enlarged side view of the rim of the opening in contact with the sealing lip following attachment.

[0028]FIG. 6 is an illustration of the self centering advantage of the present invention.

[0029]FIG. 7 is a perspective view of the longitudinal ribs on the outer surface of the annular skirt portion.

[0030]FIG. 8 is a perspective view of the pilfer band alone.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0031] Various other objects, features and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description of the preferred embodiment of the invention.

[0032] Preferably, the plastic closure according to the present invention provides an improved cap that can be easily applied to a container and forms a seal with the container capable of high-pressure retention. The cap can be easily manufactured by injection or compression molding and is suitable for use in both carbonated and non-carbonated beverage applications or for any container requiring a hermetic seal.

[0033] Referring to FIG. 1, the cap 10 attaches to container 1 and covers opening 2. Not shown in the drawing is that there is, for example, atmospheric pressure outside of the container, and inside the container the contents are under pressure. Hereinafter the atmospheric pressure will be referred to as P2 and the pressures inside the container will be referred to as P1.

[0034] The container 1 is composed of preferably, but not only of plastic and includes a main section where the contents (i.e. soda) are held and a neck 3 through which the opening 2 is defined. External threads 19 are constructed proximate to the rim 30 of the neck. A pilfer breaking member 17 a is constructed adjacent to the threads along the longitudinal axis of the neck between the threads and the container. A neck base 21 is constructed adjacent to the pilfer breaking member along the same axis.

[0035] The cap 10 as indicated in FIG. 1, is preferably formed of plastic and removably attaches to the neck 3. The cap is composed of a top wall portion 12 and an annular skirt portion 14. The top wall portion comprises an inner surface 20 that covers the opening 2 and the sealing lip 22. The annular skirt portion has internal threads 16 that cooperate with the external threads 19 of the neck 3. The annular skirt portion also supports a plurality of longitudinal ribs 18, as will be discussed below, around the outer surface. Additionally, a pilfer band 17 is connected to the bottom of the annular skirt portion and will also be discussed below.

[0036] Referring to FIG. 2, a detailed view of the top of the annular skirt portion and the sealing lip 22 is shown. As indicated, the sealing lip actually comprises a first circular rigid member 26 and a second circular rigid member 24 concentric with the first rigid member. The first and second rigid members are radially separated and symmetric on opposite sides of a circular line 29, along their entire lengths. The term “rigid” here means that, due to the shape and material composition of the members 24 and 26 they have sufficient rigidity to move the rim into proper alignment, as described below with reference to FIG. 6.

[0037] Each rigid member has an inner surface 27, 28, which respectively engages with the inner or outer surface of the rim of the opening 30 during application of the cap. Specifically, the inner side 27 of the first rigid member cooperates with the inner edge of the rim 32 and the outer side 28 of the second rigid member cooperates with the outer edge of the rim 31. As shown in FIG. 2, the inner surfaces of the rigid members, in a direction away from the line 29 where the rigid members meet at the tops thereof, taper away from one another.

[0038] The manner in which the present invention is intended to be used is illustrated in FIGS. 3 and 4. As the cap is placed above the opening, the internal threads 16 of the cap can cooperate with the external threads 19 of the neck of the container. The cap is screwed onto the container until the rim of the opening comes into contact with the sealing lip 22. This is made possible by the geometries of the cap and the opening as shown in FIGS. 3 and 4.

[0039] The radius of the center of the rim RE is less than the approximate radius of the external threads R_(et). Similarly, the radius of the center of the sealing lip R_(SL) is less than the radius of the internal threads of the annular skirt portion R_(t). Moreover, the radius of the sealing lip R_(SL) is approximately equal to the radius of the rim of the opening R_(E) and the radius of the internal threads is approximately equal to the radius of the external threads. Thus, the respective parts of both the neck of the container and the cap are aligned.

[0040] Referring now to FIG. 5, the interconnection of the rim of the opening 30 with the sealing lip 22 is shown. FIG. 5a illustrates the rim approaching the sealing lip and FIG. 5b shows the rim having contacted the sealing lip. Note that in FIG. 5b contact points C1 and C2 create a double seal that prevents leakage from the container to an area external the container. Therefore, the pressure inside the container P1 can be retained against the pressure P2.

[0041] Still referring to FIG. 5b, note that the invention does not contemplate that the seal created by the interaction and cooperation of the first and second rigid members with the rim of the opening must include a contact point between the rigid members with the uppermost edge of the rim such that height, h, equals 0. The seals created by contact points C1 and C2 provide effective sealing properties.

[0042] Referring now to FIG. 6, one of the advantages of the present invention is shown. As noted above, a defect in the prior art was that linerless devices will not form a reliable seal due to a tendency to contact the seal in an offset manner. The present invention provides a solution for that problem. FIG. 6 illustrates the approach toward the opening of the container of the rigid members in various positions a, b, c, and d, where position a is offset by a distance x from position d. Upon contact with one of the rigid sealing members 24 or 26, the rim will be forced to move into proper position as shown. This action is bidirectional since either of the rigid members 24, 26 can act on the rim. Therefore, the reliability of the seal is increased.

[0043] Referring now to FIG. 7 the longitudinal ribs 18 mentioned above will be described. The longitudinal ribs are arranged in an appropriate pattern so as to create friction between the annular skirt portion 18 and the surface of whatever is turning the cap. As shown in FIG. 4 the longitudinal ribs can comprise small rectangular members extending down the longitudinal axis of the annular skirt portion.

[0044] Referring now to FIG. 8 the pilfer band 17 mentioned above will be described. The pilfer band is connected to the bottom section of the annular skirt portion by connection members 34. It extends below pilfer breaking member 20 and above neck base 21. A breakaway member 33 locks it in place. The pilfer band can be attached to the annular skirt portion before the cap is first placed on the container and is configured to break away from the annular skirt portion when the cap is first removed under a torsional force. The pilfer band which is intended to provide added security and safety to consumers of the contents of the container is thereafter maintained between pilfer breaking member and neck base 21.

[0045] The container material, while not particularly limited, may include any thermoplastic or thermosetting polymer resin known to those in the container arts. Preferably container compositions include polypropylene, polyethylene, polystyrene and the like. The container may be molded in accordance with known methods. These include blow molding, compression molding, vacuum molding, thermoforming and the like.

[0046] The cap is preferably comprised of a plastic composition comprising at least one thermoplastic polymer resin although other materials may be used. This polymer resin should be selected from the group consisting of polypropylene, polyethylene, copolymers of polypropylene and polyethylene and combinations thereof. The polyethylene is selected from the group consisting of linear high density, low density polyethylene and combinations thereof.

[0047] Numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein. 

1. A cap, which can be attached to a container having an annular opening, comprising: a top wall comprising an inner surface including a sealing lip having first and second rigid members which, in a direction from a point between them to tops thereof, taper away from one another; and an annular skirt portion, disposed along an outer circumference of the top wall, said annular skirt portion comprising internal threads, wherein: the first and second rigid members are configured to provide a bidirectional centering force on the opening of the container.
 2. A cap according to claim 1, wherein a cross-section of the sealing lip comprises: a first rigid member, a second rigid member, which is symmetric with the first member about a center line therebetween.
 3. A cap according to claim 1, wherein the cap is composed of a plastic composition.
 4. A cap according to claim 3, wherein the plastic composition comprises at least one thermoplastic resin.
 5. A cap according to claim 4, wherein the thermoplastic polymer resin is selected from the group consisting of polypropylene, polyethylene, copolymers of polypropylene and polyethylene, and combinations thereof.
 6. A cap according to claim 5, wherein the polyethylene is selected from the group consisting of linear polyethylene, high density polyethylene, and low density polyethylene, and combinations thereof.
 7. A cap, which can be attached to a container having an annular opening, comprising: a top wall comprising an inner surface including a sealing lip having first and second rigid members of substantially equal rigidity, which, in a direction from a point between them to tops thereof, taper away from one another; and an annular skirt portion, disposed along an outer circumference of the top wall, said annular skirt portion comprising internal threads.
 8. A cap according to claim 7, wherein a cross-section of the sealing lip comprises: a first rigid member, a second rigid member, which is symmetric with the first member about a center line therebetween.
 9. A cap according to claim 7, wherein the cap is composed of a plastic composition.
 10. A cap according to claim 9, wherein the plastic composition comprises at least one thermoplastic resin.
 11. A cap according to claim 10, wherein the thermoplastic polymer resin is selected from the group consisting of polypropylene, copolymers of polypropylene and polyethylene, and combinations thereof.
 12. A cap according to claim 11, wherein the polyethylene is selected from the group consisting of linear polyethylene, high density polyethylene, and low density polyethylene, and combinations thereof.
 13. A cap, which can be removably attached to a container having an annular opening, comprising: a top wall comprising an inner surface including a sealing lip having first and second rigid members which, in a direction from a point between them to tops thereof, taper away from one another; and an annular skirt portion, disposed along an outer circumference of the top wall, said annular skirt portion comprising internal threads, and a means on the top wall for providing a bidirectional centering force on the opening of the container. 